This invention relates to a rubber plug that is used in a waterproof connector for forming a water-tight seal between a cavity in the connector housing and an electric wire.
One conventional rubber plug is shown in FIG. 4. A rubber plug 30 has a tubular shape as a whole. Annular outer peripheral lips 32 are formed on an outer periphery of the rubber plug, and annular inner peripheral lips 33 are formed on an inner periphery of the rubber plug. The rubber plug 30 is fitted on an electric wire 40 fixedly connected to a rear end portion of a metal terminal 45. The rubber plug is inserted into open end 43, together with the metal terminal 45 and the wire 40, into a cavity 42 of a connector housing 41. When the rubber plug is thus inserted, the outer peripheral lips 32 are pressed against an inner peripheral surface of the cavity 42, so that a water-tight seal is formed between the rubber plug 30 and the inner surface of the cavity 42. Also, the inner peripheral lips 33 are pressed against an outer peripheral surface of the wire 40, so that a water-tight seal is formed between the rubber plug 30 and the wire 40. With this arrangement, water is prevented from intruding into the cavity 42.
Generally, depending on the manner of arranging the wire 40, the wire 40 may be bent laterally at the open end 43 of the cavity 42, as shown in FIG. 5. In such a case, in the above conventional rubber plug 30, a force bending the wire 40 acts on the rubber plug 30, so that the rubber plug 30 is compressed at a region disposed inwardly of this bent portion. Therefore, at the opposite side, that is, at a region disposed outwardly of the bent portion, a gap 44 develops between the outer peripheral lips 32 of the rubber plug 30 and the inner peripheral surface of the cavity 42. This has the undesirable effect of allowing water to enter into the cavity 42. In addition, the wire 40 comes in contact with the sharp edge 50 of the connector, which may cause damage to the wire.